The invention relates to a method for the control of a monitored zone, in particular at transport devices for objects, wherein the monitored zone is scanned by means of at least one spatially resolving sensor, in particular a laser scanner and/or a camera system, and the positions of object points in the monitored zone are determined.
The invention moreover relates to a process device, in particular a transport device for objects, comprising at least one spatially resolving sensor for the control of a monitored zone associated with the process device.
The invention furthermore relates to a sensor for the control of a monitored region, in particular at transport devices for objects.
It is frequently necessary on the conveying of objects by means of transport systems which are made, for example, as roller conveyors or a conveyor belt, when the transported objects are transferred from one zone into another zone, to prevent persons from intruding or entering into the transfer zone also called a transport lock or even passing through this transfer zone. To ensure this safety of persons, the transport locks are currently secured by combinations of light barriers, light grids and laser scanners providing variable protected fields.
The transport locks are moreover usually provided with additional sensors for automation and control tasks in order, for example, to carry out overhang controls, checks of pallet heights, checks of the degree of filling of pallets or length measurements on the transported good. Separate sensor systems have therefore previously been used for the automation and/or control functions, i.e. for the normal process control, on the one hand, and for the required safety functions, on the other hand, which means a relatively high installation and connection effort and is not least associated with high space requirements. In addition, a substantial effort is required to link the normal process control with the security control.
A method and an apparatus for the control of a pre-determined monitored zone are known from DE 44 11 448 A1. A laser scanner, in particular arranged close to the edge of a monitored zone to be controlled, determines spacing contour functions and compares these with stored reference contour functions each representing an expected object contour. A check is made within the framework of pre-determined tolerance limits whether a determined spacing contour function coincides with a reference contour function or not. Although this known device is capable of reliably distinguishing persons intruding into the monitored zone from permitted objects, it is a disadvantage here that objects which are actually permitted can also trigger the emission of a warning signal if they do not pass through the monitored zone in the manner pre-determined by the previously obtained reference contour function determined, for example, by a teaching procedure. An object expected, for example, in the center of a conveyor belt, but actually lying in the edge region on the transport belt when passing through the monitored zone results in the emitting of a warning signal with the known control methods due to the deviation of the measured spacing contour function from the stored reference contour function even though the object is an object permitted per se. The lack of flexibility of the solution known from DE 44 11 448 A1 is consequently in particular a problem.